The fate of absorbed light in the facultative CAM plant Portulacaria afra Jacq (L) subjected to drought.

Crassulacean acid metabolism (CAM) is a photosynthetic pathway typical of plants well adapted to water-limited environments (Guralnick et al., 1984, Plant Physiol, 75: 454-45; Guralnick et al., 1984, Plant Physiol, 76: 643-646). In some species (facultative CAM, C3/CAM cycling), CAM is induced by environmental factors such as water stress (Tin & Hanscom III, 1977, Plant Physiol, 59: 511-514). Portulacaria afra (L.) is a perennial, C3/CAM cycling plant that under prolonged water stress shifts from CAM to CAM-idling characterized by complete stomatal closure and reduced diurnal changes in titratable acidity. This work evaluates CAM activity modulation and the fate of the absorbed light by PSII in plants exposed to a long dry period and re-watering.